The invention relates to a method and a device for treatment of substantially spherical balls, in particular metal balls, such as steel balls for rolling bearings, by gentle mechanical treatment in the presence of a treatment fluid, particularly a cleaning liquid.
In order to efficiently clean steel balls, which have previously been mechanically treated so as to obtain an exact spherical shape, it is insufficient to merely wash the balls in a liquid bath. In addition thereto, a certain, yet gentle mechanical treatment is necessary, e.g. by brushing or rubbing with a soft material, so that even solid impurities are removed from the surfaces of the balls.
The DE Offenlegungsschrift No. 2 262 292 discloses a device wherein rolling bearing balls are treated between two discs or plates rotating eccentrically and in opposite directions and both being provided with a soft cushion of foamed plastic or the like. Hereby the balls will roll out spirally from the centre. However, it has turned out that the balls spontaneously roll about an axis which is parallel to the plane of the plates, and therefore the balls are not being treated around the entire surface, since the cap-shaped surface portions around said axis never touch the foamed plastic covered discs. In order to eliminate this draw-back, the known device is provided with recesses in the foamed plastic cushion of the upper plate. The diameter of these recesses is greater than that of the balls, the idea being that the balls on their way out towards the periphery shall randomly reach and temporarily stay in at least some of these recesses, whereby they will hopefully change their orientation before re-entering and rolling on between the foamed plastic layers of the plates.
One disadvantage with this arrangement is that the balls can get stuck in a recess and remain there until they are pushed away by another ball, whereby the surfaces of the finished balls can be damaged. Furthermore, there is no guarantee that the balls will re-orient themselves in the recesses.
The object of the invention is therefore to achieve a reliable method and device ensuring every ball to become uniformly fluid-treated over its entire surface and to be kept separated from the other balls during the process.
An important basic feature is thus to let the balls move between two mutually rotating discs while being forcedly guided along a spiral path with such a skidding that each ball is forced to rotate around an axis that constantly changes its direction, whereby the entire surface of the ball will be treated. Furthermore, a well-controlled transport of the balls one by one is made possible along the respective spiral guide. Thereby, the balls can be separated from each other and they will not hit each other or any of the walls in the apparatus. All the time, the balls contact the two discs as well as the spiral guide, partly by rolling engagement and partly while skidding.